gstlal_inspiral_coinc_extractor_dag: port to ligo-lw dbtables.workingcopy

This program was not ported as part of 6280612b, with the following rationale:

those two codes are missing the required clean-up function calls, and leak working copies out into scratch disks. since I don't know what behaviour was intended, I can't correctly migrate them to the new mechanism.

It will be required to convert this before the next version of python-ligo-lw is released. That commit can be used as a conversion guide.

I have assigned this to who I believe is the code owner. Feel free to reassign this if I have assigned this to the wrong person.